Car: Tesla Native Spotify app or (shock horror) the radio.

Kitchen: Airplay from a phone into a Raspberry Pi running shairpoint-sync with an amplifier HAT and a pair of old Sony mini system speakers.

Office:VLC, Plex or Spotify through an old RME USB->AES3 interface or a Technics SL1210Mk7 turntable and a Philips CD624 CD Player via a small Sonifex monitor controller and PPM. Then into a pair of Tannoy Reveal 8D's which have been retrofitted with MiniDSP PWR-ICE 125W plate amps. Or a pair of HD25's.

That's all I have, currently. But assuming I add more rooms, I'll probably just use more Pi's and amp HAT's.